Railway signaling system



March 1943- o. s. FIELD- RAILWAY SIGNALING SYSTEM Fild Feb. 14, 1941 2Sheets-Sheet 1 FIGJ FIG-.2.

IINVENTO March 9, 1943. o, s, FIELD RAILWAY SIGNALING SYSTEM 2 SheetsSheet 2 Filed Feb. 14, 1941 1 INVENT' Patented Mar. 9, 1943 RAILWAYSIGNALING SYSTEM Oscar S. Field, Rochester, N. Y., assignor to GeneralRailway Signal Company, Rochester,

Application February 14, 1941, Serial No. 378,966

11- Olaims. (Cl. 246-53) This invention relates in general to railwaysignaling systems and has more particular reference to wayside signalingsystems employing type SC search light type signals.

The type SC search light signal is constructed and operates as disclosedin the Field application, Ser. No. 361,060, filed October 14, 1940.

This type SC signal has a single spectacle carrying a plurality ofcolored glasses through one of which at a time light from a single lightsource is directed to give a signal indication. The spectacle'is movedto various indicating positions by two separate mechanisms or relayswhich also operate various contacts and because of this construction,many of the usually employed relays such as line relays, repeatingrelays, etc., generally used in signaling systems, can be dispensed withsince the operating mechanisms of the signals themselves can serve theadded function of these otherwise necessary relays.

Further objects, purposes and characteristic features of this inventionwill appear as the description progresses, reference being made to theaccompanying drawings, showing solely by way of example, and in no waywhatsoever in a limiting sense, several forms of the invention. In thedrawings:

Fig. l is a diagrammatic representation of one lorm of the invention.

Fig. 2 is a diagrammatic representation of a second form of theinvention.

Fig. 3 is a diagrammatic representation 'of a signaling system employingalight signal of the type SA form and is shown forthe purpose ofclarifying the disclosure of the invention.

Fig. 4. is a diagrammatic representation of a third form of theinvention.

In Fig. 1 is shown an application of the type SC signal used in asignaling system of the polarized type in which no line wires areemployed. In Fig. l, the track rails 6 comprising a stretch of singletrack, are separated into track sections by insulating joints I to formsections, the complete section 2 with the entrance end of section 3 andthe exit end of section I being shown, trafiic being east boundas'indicated by arrow 8 Connected across the exit end of each tracksection is a battery B2 controlled by a pole changer having contacts 2|and 22 of the relay RYE. of signal S2 which is a signal of the searchlight SC type. The current feed to the exit ends of the sections includesuitable adjustable reactances 23.

Connected across the entrance end of each track section, as section 2 isa track relay TR2 which is shown as of the polar retained neutral type,and can be as disclosed, for example, in the Bennett patent, No.1,969,058, granted August 7, 1934. This retained type of relay isconstructed as diagrammatically shown to retain its neutral contact 24against releasing when the energizing polarity is changed so as to causeits polar contacts 25 and 26 to move from one side to the other.

The signal employed in this form of the invention and denoted by S2 hasa spectacle SP operated by a red-yellow relay RYR and by a yellow-greenrelay YGR in the manner as described above.

With track section 2 unoccupied as shown, the signal assumes theposition as shown to display the green indication, the two controlrelays being energized as is obvious from the drawings.

If we assume that a train occupies section 2 the track energy will beshunted away from the trackrelay TRZ to cause its contact fingers 24, 25and 25 to assume their retracted positions, whereby to deenergize bothof the operating relays of the signal and cause it to move to a positionto display its red indication.

With relay RYR deenergized, what can be termed reverse polarity isplaced on the upper rail of the section to the rear, through contactfinger 22 and back point, etc., whereby to cause the signal attheentrance to section i to display its yellow indication. With reversepolarity energy on the track, the track relay moves its polar armatureand fingers to the right, whereby to energize the red-yellow relay anddeenergize the yellowgreen relay.

The block to the rear of block I will receive normal polarity on theupper rail so as'to energize both of the corresponding signal relays andcause the signal to display a green indication. The same occurs for allsignals to the rear thereof, providing no occupancy be present. a

The track relays as relay TR2 have been shown as of the polar retainedneutral type but in many cases, the red-yellow relay of the signal inquestion is slow enough to release or can be made slow enough to releaseso that the time during which the red-yellow relay is deenergized due tothe neutral contact finger as 24 of the track relay is away from itsfront contact is not long enough to allow it to release and produce aflash of the red indication. If the red-yellow relay is not slow enoughin releasing to bridge this period of deenergization the retained typeof track relay can be used whereby the deenergization of relay RYR ismerely of the duration while the polar contacts move from one positionto the other. These polar contacts move very rapidly and are of the snapaction type whereby there can be no chance whatsoever of a flash of thered occurring under the conditions referred to just above.

In Fig. 2 there is shown a slightly modified form of the inventionwhereby a polarized signal of the SC type is employed in connection withpolarized track circuits.

In this form of invention a stretch of single track is constituted bytrack rails fi 'having insulating joints 1 with travel being consideredin an easterly direction as indicated by arrow 8 In this modification, asignal as S2 is positioned at the entrance end of each section and is ofthe SC type. This signal difiers slightly from that described above inthat the yellowgreen relay YGR. is polarized by a permanent magnet 30whereby to cause the yellow-green relay to respond only to energizationof what may be termed normal polarity. The red-yellow relay RYR isnon-polarized but is connected across the output side of a full-waverectifier 3i! whereby to prevent it releasing its armature whenenergizing polarity is changed. The operation of this polarized type ofsignal is disclosed in detail in theField application referred to above.In brief, the signal spectacle SP is biased to display the redindication, is moved to display the yellow indication when the signal isenergized by current of reverse polarity and to display the greenindication when the signal is energized with current of normal polarity.

The parts are shown in Fig. 2 in the positions and conditions theyassume when the track is unoccupied. Current of normal polarity from abattery (not shown) is connected to the upper rail by wire 3| toenergize track relay TR2 to pick up its neutral contact finger 3| andposition its polar contact finger 32 to the left. This applies currentof normal polarity to the windings of the two signal control relays,through a circuit including polar contact finger 32 of relay TR2 tothereby position the spectacle of the signal S2 to display its greenindication.

If we now assume that section 2 be occupied by a vehicle, relay TRZ isdeenergized to deenergize both of the operating relays of the signal S2to thereby cause it to display its red indication.

With relay RYR. deenergized, current of reverse polarity is applied tothe exit end of block I immediately to the rear to thereby cause thesignal for this block to display its yellow indication.

The block immediately to the rear of block l and all blocks to the rearthereof, assuming unoccupancy, are supplied with normal polarity sincethe red-yellow relays are energized, whereby to cause the signals todisplay their green indications.

It is clear that the signal upon changing from yellow to green due to achange of the polarity applied to the track section, is momentarilydeenergized. The red-yellow relay of such signal is slow in releasingdue to the rectifier connected across its winding whereby to bridge overthis brief period of deenergization and retain the yellow indicationuntil the green indication is put in force, thus to avoid any flash ofthe red indication occurring between a yellow and green indication. Italso can be noted that no relays or other apparatus is required inaddition to the signal of this SC type, except the sources of energy andconnecting wires and the track relays.

In the form as shown in Fig. 2, the track relay has been shown as of thepolar retained neutral type but this may not be necessary andparticularly so in the polarized type of signal as shown in Fig. 2,wherein the rectifier 30 imparts slow release characteristics to thered-yellow rey.

Furthermore, in the form of Fig. 2, the track relays can be dispensedwith and the signal energizing circuit connected across the track rails.

Referring now to Fig. 3, there is here shown a stretch of trackconstituted by track rails 6 divided intoisolated track sections byinsulating joints 1 with traffic considered as moving eastward, asindicated by arrow 8 To exemplify this form of invention, the signal isshown as of theSA type so as to aid an understanding of the advantagesthereover of the SC type of signal employed in a corresponding signalingsystem. Between successive signals as S2 and S3 there are two separatetrack sections, as 2 2 constituting a split section in a well recognizedmanner. With such a split section a track relay as TR2 is placed acrosseach end of the split section with intermediate insulating joints andtrack batteries 40 and 4|.

The type SA signal here employed is constructed and operates asdescribed in the Murphy patent, No. 2,156,637, granted May 2, 1939.Briefly, it includes a spectacle 42 carrying colored roundels G, R andY, respectively colored green, red and yellow! and positioned in theorder named. That is, the red roundel is between the green and yellowroundels. The spectacle is biased to normally assume a position oppositea light source 42a, so as to display its red indication. Upon beingenergized with current of reverse polarity its winding 43 operates thespectacle to a position to display its yellow indication, and whenenergized with current of normal polarity the spectacle is moved todisplay its green indication. The spectacle on movingoperates contactors44 and 45 by means of pins 46 and 41 to place energy on a circuitincluding wire 48 when it is in either its green or its yellowindicating position.

Associated with the signal is a repeater relay YGP2 which is connectedin the circuit including wire 48 whereby to constitute a yellowgreenrepeater relay and be energized when its signal is displaying eitheryellow or green. This repeater relay, when energized, places current ofpositive polarity on the signal winding immediately to the rear and whendeenergized places current of negative polarity on this winding througha circuit including front contacts in series of the two track relays ofthe section to the rear.

For example, the repeater relay YGP3 is shown as being energized wherebyto place current of normal polarity on winding 43 of signal S2 through acircuit including contact finger 49 and front point of repeater relayYGP3 contact finger 50 and front point of track relay 'I'R2 contactfinger 5| and front point of the other track relay TR2 and the winding43 of signal S2 This current of normal polarity causes the signal todisplay its green indication and to likewise cause all signals to therear thereof, assuming'non-occupancy, to also display their greenindications.

If we now assume that a vehicle occupies section 2 the energizingcircuit for winding 43 is broken by one or the other or both-of thetrack relays TR2 whereby to cause the signal to display its redindication. Through contact finger 52 and back point of relay YGP2current of reverse polarity is placed on the winding of the signalnext-to the rear. This signal'thus displays its yellow indication andcauses current of normal polarity to be placed on the control winding ofthe signal next in the rear thereof, whereby to cause it to display itsgreen indication.

It should be noted that the pole changing of energy on the signalcontrol winding at one location, by the signal at the location next inadvance, is accomplished through a repeater relay as YGP2 and not bymeans of the contacts in the signal itself such as the contacts 44 and45. If this pole changing function were handled by the contacts withinthe signal mechanism, with a signal of this construction, that is, an SAtype signal, a signal which isdisplaying its yellow indication and ispole changed to display its green indication would necessarily in movingfrom yellow to green momentarily change the polarity on the signal nextto the rear which is displaying the green indication to cause it toshift to its yellow indication and then back to its green indication.This shift would change the polarity on the signal next to the rear,etc., whereby there would be an undesirable momentary shift of'all ofthe clear signals through the red to the yellow and back again to thegreen upon every change in traffic conditions. By using the slow releaseyellowgreen repeater relay this faulty operation'is overcome but it isat the expense of employing a separate relay additional to thesignal'itself when the SA type of signal is employed.

Considering more specifically the possible use of the signal contactsthemselves for performing the pole changing function, we can assume thator normal polarity of current is applied to wire 48, and or reversepolarity of current is applied to the stop 55.

Now let us assume that a vehicle occupies a block so as to put thesignal at its entrance at red with the next to the rear at yellow, andthe next, etc., at green, and further, assume that the vehicle advancesto the next block forward. It should be kept in mind that with the polechanging function carried by the signal contacts themselves, a signal atred places current of reverse polarity on the signal next to the rear tomake it display yellow, and that a signal at yellow places current ofnormal polarity on the signal next to its rear to make it display green;and further, that the green signal also places current of normalpolarity on the signal next to its rear, etc. When the train advances tothe next block, the former red signal receives current of reversepolarity due to the signal next in advance having gone to red. Likewise,the former yellow signal receives current of normal polarity from theformer red signal which is now yellow to produce a green indication.This last signal, passing from yellow to green due to current of normalpolarity, must necessarily pass through the red indication stage, due tothe construction of the signal andits spectacle in so doing placescurrent of reverse polarity on the signal next to the rear. I

Thus, the first green signal, upon a train advancing a block, is firstdeenergized, thenis-energized with current of reverse polarity,'fandthen is energized with current of normal polarity. Ac-

- arrow 8 cordingly, this signal not onlymust bridge a period of timewhen there is no energy on it but also a period of time when current ofreverse polarity is on it, and accordingly, it will momentarily displaya yellow indication and in thus passing from green to yellow will affectthe green signal next in the rear thereof in the same manner.

From the above it can be seen that not only should the signal be slow torespond in order to bridge a period of time of deenergization but itmust overcome a reversal in the polarity of the-current of energization,and thus this type of signal is not at all suited to carry the polechanging function by its own contacts. The yellow-greenrepeater relay,as described above, is slow to release and is always energized bycurrent of the same polarity,-and,hence, the first green signal to therear of the train, upon the train moving forward to the next block, notonly does not have its-polarity of energization changed but does nothave its energization interrupted since the yellow-green repeater relayholds up while the spectacle of the signal ahead moves from the yellowto the green position. Thus, the requirements for a properly operatingsystem is a'relay of this type which not only is slow to release'andhence can bridge over agap of deenergization, but is so arranged that itis never reversely energized.

With reference to Fig. 4, the system here shown is'the same, in general,as that shown in Fig. 3 anddescribed above, except that the signal ofthe system of Fig. 3' is of the SA type and, as explained, requires ayellow-green repeater relay for pole changingthe-control circuit for thesignal to the rear. In Fig. 4, the signal employed is of the polarizedSC type, the same as disclosed and described with reference to Fig. 2,and with it no additional pole changing relay is required.

In Fig. 4 the stretch of single track is constituted by track rails 6separated into track sections by insulating joints 1 with traffic beingconsidered eastbound, i. e., in the direction of As described inreference to Fig. 4, the signal at each location is controlled through aline circuit extending to the signal next in advance and is eitherdeenergized, energized with current of reverse polarity, or energizedwith current of normal polarity. For example, signal S2 at the entranceto sections 2 is controlled by signal S3 of the section next in advancethrough a line circuit including contact Bil, wire 6i, contacts 62 and63 of track relays TR2 and the two control windings in signal S2 thatis, the

red-yellow relay RYR and the yellow-green relay YGR.

With the signal arranged so that when current of negative or reversepolarity is applied to it, the red-yellow relay but not the yellow-greenrelay is energized, and when current of positive or normal polarity isapplied both of these relays are energized, it can be seen that signalS4 at the entrance to the block occupied by the vehicle 64 isdeenergized due to track relay EH4 being shunted out, and thus itdisplays its red indication.

The signal next to the rear is energized by cur-- rent of reversepolarity through contact finger 65 and back point of the red-yellowrelay of the signal ahead to cause signal S3 to display its yellowindication. With signal S3 having its redyellow relay energized, currentof normal polarity is applied to signal S2 to thereby cause it todisplay its green indication. The signals to the rear, assumingnon-occupancy, all display green indications.

t can be noted that the red-yellow relay of each signal such as relayRYR of signal S2 is connected to be energized through a full-waverectifier 66 whereby its energization is always in the same directionregardless of the polarity of current applied to the signal as a whole.Furthermore, due to the rectifier and also due to the inherent structureof this relay, it is slow to release.

Thus this red-yellow relay, which functions to move the spectacle of itssignal, also has the unidirectional energization and the slow releasecharacteristics of the yellow-green repeater relay such as relay YGP2employed in connection with the type SA signal of Fig. 3. Accordingly,the pole changing function can be handled by the red-yellow relay of thetype SC signal in addition to its other function of operating thespectacle and thus obviate any necessity or desirability for anadditional yellow-green repeater relay as is absolutely essential whenthe type SA signal is employed.

In the system as shown in Fig. 4, upon the cation. It should be notedthat signal S3 on having the polarity of the applied current changedfrom reverse to normal does not have the direction of energization ofits red-yellow relay reversed, and hence the red-yellow relay of thissignal S3 holds up during the momentary period of its deenergizationwhile contact finger 65 of signal S4 moves from its back to its frontpoint. Thus, the normal polarity of energization of the first signaldisplaying green to the rear of the vehicle, that is, signal S2 is notdisturbed, and there is no possibility of any momentary tumble-downeffect throughout the system.

Accordingly, the type SC signal can be employed in systems whereformerly the type SA signal was employed, to manifest advantage since itobviates any necessity for any yellow-green repeater relay, as must beused in connection with the type SA signal.

In the various systems described above, it is of course to be understoodthat various modifications and refinements can be applied thereto ifdesired such as approach control means for the coding or for theenergization of the light sources of the signals, or both, if desired.Furthermore, various coding means and various arrangements of tracksections different from those shown, can be employed if desired. Forexample, the stretch of track between adjacent signals can include notonly two track sections as shown in Figs. 3 and 4, but one only, ifdesired, or more than two, if desired.

The above rather specific description of several forms which thisinvention can assume is given solely by way of example, and isnotintended in any manner whatsoever in a limiting sense. It is to beunderstood that various modifications, adaptations, and alterations maybe applied to meet the requirements of practice without in any mannerdeparting from the spirit or scope of this invention, except as clearlylimited by the appended claims.

Having described my invention, I now claim:

1. In a wayside signaling system for railways, in combination, a stretchof track divided into electrically isolated blocks, a search lightsignal at the enerance end of each block, each signal including aspectacle movable progressively from a biased most restrictive position,through a lesser restrictive position, to a least restrictive position,a first and a second relay in the signal, means operatively connectingthe relays to the spectacle so as to move the spectacle to its lesserrestrictive position when the first relay is energized, and to move itto its least restrictive position when both relays are energized, meanscontrolled by said first relay for placing energy of one or the otherpolarity on the exit end of the block next to the rear in accordancewith traffic conditions, a polar neutral track relay associated witheach signal, and means effective to energize said first relay when theassociated track relay is energized with either polarity of current, andeffective to energize said second relay only when the associated trackrelay is energized with current of one of said polarities.

2. In a wayside signaling system for railways, in combination, a stretchof track divided into electrically isolated blocks, a search lightsignal at the entrance end of each block, each signal including aspectacle movable progressively from a. biased most restrictiveposition, through a lesser restrictive position, to a least restrictiveposition, a first and a second relayin the signal, means operativelyconnecting the relays to the spectacle so'as to move the spectacle toits lesser restrictive position when the first relay is energized, andto move it to its least restrictive position when both relays areenergized, means controlled by said first relay for placing energy ofone 01' the other polarity on the exit end of the block next to therear, a polar neutral track relay associated with each signal, magneticmeans for retaining the neutral armature of the track relay in attractedposition during change in polarity of energization of the relay, andmeans effective to energize said first relay when the track relay isenergized with current of either polarity and effective to energize saidsecond relay only when the polar relay is energized with current of aparticular one of said polarities.

3. In a wayside signaling system for railways, in combination, a stretchof track divided into electrically isolated blocks, a search lightsignal at the entrance end of each block, each signal including aspectacle movable progressively from a biased most restrictive position,through a lesser restrictive position, to a least restrictive position,a first and a second relay in the signal, means operatively connectingthe relays to the spectacle so as to move the spectacle to its lesserrestrictive position only when the first relay is energized, and to moveit to its least restrictive position only when both relays areenergized, means polarizing said second relay so that it is responsiveto current of one polarity only, rectifying means connecting the tworelays in a common circuit in such manner that regardless of thepolarity of current applied to the common circuit said first relay isenergized by current flowing in a particular direction, means controlledby said first relay for placing energy of one or the other polarity onthe exit end of the block next to the rear, and means for energizingsaid common circuit with current of a polarity varying with the polarityapplied to the exit end of the associated block.

4. In a wayside signaling system for railways, in combination, a stretchof track divided into electrically isolated blocks, a search lightsignal a biased most'rest'rictive position, through a lesser restrictiveposition, to a least restrictive position,

a-first and a second relay in 't-he signaL' means i operativelyconnecting the relays to thespectacle so as to move the spectacle to itslesserrestrictive position when the first relay only is energized, andto move it to its least restrictive position when both relays areenergized, means polarizing said second relay so as to be responsive tocurrent of one polarity only, rectifying means connected with its inputside to be energized in common with the second relay and its output sideconnected across the first relay so that the two relays are in a commoncircuit, means controlled by said first relay for placing energy of oneor the other polarity on the exit end of the block next to the rear, apolar retained neutral relay connected across the entrance end of eachblock, and means controlled by the polar relay for energizing the commoncircuit with current of a polarity varying with the polarity applied tothe polar relay.

5. In signaling systems for railways, in combination with a stretch oftrack separated into electrically isolated sections, a light signal atthe entrance end of each section, each light signal including aspectacle movable from a biased, most restrictive postion, through anintermediate position, to a least restrictive position, two separaterelays in the signal, means operatively connecting the relays to thespectacle so that the spectacle is moved to the intermediate positionwhen one only of said relays is energized, and to the least restrictiveposition when both of said relays are energized, a pole changer operatedby said one relay, means connected to said one relay to rectify allcurrent energizing said one relay and control circuit means connectingthe pole changer of each signal to the two relays of the signal next tothe rear.

6. In combination With a railway track divided into sections byinsulating joints, a track circuit for each section including a normallyenergized track relay, a search light signal at the entrance to onesection and having two electro-magnets one of which is energizable onlyin response to current of one polarity and the other of which isenergizable in response to current of either polarity, a line circuitextending along said one section, and energized by current of one or theother polarity in accordance with traffic conditions in advance, forcontrolling the electromagnets of said signal, said line circuitincluding a contact closed only if the track relay for said one sectionis energized, a second signal to the rear of said one signal, and a linecircuit for energizing said second signal by current of one or the otherpolarity, and including pole changer contacts controlled by the saidother electro-m-agnet of said search light signal.

7. In signaling systems for railways, in combination with a stretch oftrack separated into electrically isolated sections, a light signal atthe entrance end of each section, each light signal including aspectacle movable from a biased, most restrictive, position, through anintermediate position, to a least restrictive position, two separaterelays in each signal, means operatively connecting the two relays tothe spectacle so that the spectacle is moved to the intermediateposition when a particular one of said relays is energized, and to theleast restrictive position only when both of said relays are energized,means --polarizing the other of said relays, of each sig- "nal, meansconnected to said one relay. in: each signal to render said one relay'slow torelease I so as to'not release due tozchangexof polarity ofenergizing-current; and circuit means connecting 'each' signal with thesignal next-to'thef rear and controlled by said one-relay of'eachysignalfor I applying-energizing current'of one or the other ---polarity to"the twor'elays of thesignal'next to the-rear, in" accordance withtranic conditions ahead.

8. In signaling systems for railways, in combination with a stretch oftrack separated into a plurality of electrically isolated sections, alight signal at the entrance end of each section, each light signalincluding a spectacle movable from a biased, most restrictive, position,through an intermediate position, to a least restrictive position, twoseparate relays in each signal, means operatively connecting the tworelays to the spectacle so that the spectacle is moved to theintermediate position when one of said relays is energized, and to theleast restrictive position only when both of said relays are energized,means polarizing the other of said relays of each signal, meansconnected to said one relay of each signal to rectify all currentapplied to said one relay, and circuit means controlled by said onerelay in each signal, in accordance with trainc conditions ahead, forapplying current of one or the other polarity to the two relays of thesignal next to the rear.

9. In a wayside signaling system for railways, in combination, a stretchof track divided into electrically isolated blocks, a search lightsignal at the entrance end of each block, each signal including aspectacle movable progressively from a biased, most restrictive,position, through a lesser restrictive position, to a least restrictiveposition, a first and a second relay in the signal, means operativelyconnecting the relays to the spectacle so as to move the spectacle toits lesser restrictive position only when the first relay is energized,and to move it to its least restrictive position only when both relaysare energized, means polarizing said second relay so that it isresponsive to current of one polarity only, rectifying means connectingthe two relays in a common circuit, and means controlled by said firstrelay for causing energy of one or the other polarity to be applied tothe common circuit of the signal next in the rear.

10. In signaling systems for railways, in combination with a stretch oftrack separated into electrically isolated sections, a light signal atthe entrance end of each section, each light signal including aspectacle movable from a biased, most restrictive, position, through anintermediate position, to a least restrictive position, two separaterelays in the signal, means operatively connecting the relays to thespectacle so that the spectacle is moved to the intermediate posi tionwhen one only of said relays is energized, and to the least restrictiveposition when both of said relays are energized, a pole changer operatedby said one relay, means connected to said one relay to rectify allcurrent energizing said one relay and control means operativelyconnecting the pole changer of each signal to the two relays of thesignal next to the rear.

11. In a wayside signaling system for railways, in combination, astretch of track divided into electrically isolated blocks, a searchlight signal at the entrance end of each block, each signal including aspectacle movable progressively from a spectacle so as to move thespectacle to its lesser restrictive position when the first relay onlyis energized, and to move it to its least restrictive position when bothrelays are energized, means polarizing said second relay so as to beresponsive to current of one polarity only, rectifying 10 meansconnected with its input side to be energized in common with the secondrelay and its output side connected across the first relay so that thetwo relays are in a common circuit, and means controlled by said firstrelay and efiective to apply energy of one or the other polarity to thecommon circuit of the signal next to the rear.

OSCAR S. FIELD.

